The AIX special handler which skips this test if unix network isn't
supported, doesn't need to be called inside the helper process.

Change-Id: I7ff2c4e6b20eceb977380294858cae63034ffe0d
Reviewed-on: https://go-review.googlesource.com/c/go/+/172160
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>